1. Field
The present invention relates to four wheel steering apparatus for vehicles and, more particularly, to a steering system specially adapted for riding lawn mowers which varies the steering angles of the wheels to significantly reduce scrubbing during a turn.
2. Description of the Prior Art
It is generally well known in the riding lawn mower industry that maintaining congruent turning angles for both the inner and outer wheels frequently causes the outer wheel to skid during a turn. Such skidding is typically referred to as "scrubbing", and is generally known to those skilled in virtually any area involving the steering of four wheeled vehicles. It is particularly troublesome when associated with riding lawn mowers, however, for scrubbing tends to damage or even destroy the underlying grass, which is an acutely unacceptable consequence.
Riding mower manufacturers have, for a number of years, alleviated the problem of scrubbing for front wheel steering systems by utilizing specially configured four-bar linkages or other generally conventional means to vary the turning angles between inner and outer wheels. On more sophisticated mowers utilizing four wheel steering systems, however, it has heretofore been difficult and expensive to provide a steering system which eliminates scrubbing of the rear wheels, or at least reduces scrubbing to an acceptable level. The physical constraints imposed by a typical rear wheel and axle assembly prevents the use of conventional scrub eliminating linkages as used for front wheel steering systems, thereby necessitating the complete re-design of the rear end and the use of costly custom components to achieve acceptable rear wheel steering. With the advantages and increasing popularity of riding mowers incorporating four wheel steering systems, particularly those with anti-scrubbing features, the high cost associated with rear wheel steering systems has recently become a significant concern.